A vote to leave the EU could bring long-term benefits for the UK after short-term uncertainty, a think-tank said today.

But Ulster University's economic policy centre said the short-term downsides of a Brexit would hit the province more than any other UK region. That was because of its land border with the Republic and the size of its agriculture sector.

And in its spring outlook, the centre said that it was not clear that existing EU support for agriculture would be replaced by support from Westminster in the event of a vote to leave on June 23.

The Department of Agriculture and Rural Development (DARD) received £635m, mainly due to single farm payments, from the EU between 2013 and 2015.

Gareth Hetherington, associate director at UUEPC, said: "The Brexit question is a real conundrum and if we are being honest, we don't know if the UK would be better off inside or outside the EU because we simply don't know what exit looks like."

But he said short-term uncertainty would impact business investment.

"In addition, the risk that we would not reach a free trade agreement with the EU cannot be discounted, but that is very unlikely given the importance of the UK market to French and German exporters," he said.

But he said leaving could bring greater flexibility to reach free trade agreements with other parts of the world, such as Asia, which were growing more quickly than the EU.

"So, in the short term the costs are likely to outweigh the benefits but in the long term the benefits could be greater," he said. The centre said the decision made by Britain would also have implications for the Republic because of the volume of trade across the border. But it's a decision over which the Republic "will have no say," the centre added.

The Republic's Taoiseach Enda Kenny has said every Irish company which exports to Britain would be told of the importance of trying to stop a 'Brexit'.